Term
| What are the Gram stain characteristics of Corynebacterium? |
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Definition
- Gram-positive rods
- not acid-fast
- pleomorphic shapes resembling "Chinese letters"
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Term
| What is the main pathogen in the USA from the Corynebacterium genus? |
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Definition
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Term
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Definition
| Any coryneform bacteria that isn't diphtheriae/ulcerans/JK |
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Term
What else does Corynebacterium diphtheriae cause other than diphtheria?
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Definition
| impetigo-like skin lesions that has little or no toxin effect; most common in tropics and among American Indians |
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Term
| What is the pathogenesis of diphtheria? |
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Definition
It begins as a local infection of the throat
- bacteria carries a phage that encodes a protein exotoxin, which spreads systemically
one molecule of exotoxin can halt protein synthesis in an entire cell |
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Term
| What are the two components of diphtheria exotoxin? |
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Definition
A: actively shuts off protein synthesis by binding to protein elongation factor 2
*can be recycled from ribosome to ribosome
B: binds to cell receptor and facilitates movement of the toxin into the cell |
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Term
| What is the D in DPT vaccine? |
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Definition
| formalin is added to diphtheria toxin to convert it into a "toxoid" which is antigenic but no longer toxic - this prevents disease but does not prevent the actual infection |
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Term
| How long is the incubation period for diphtheria? |
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Definition
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Term
| What is the clinical presentation of diphtheria? |
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Definition
- pharyngitis/tonsillitis: malaise, sore throat, fever
- grey-white patch of exudate on tonsils, uvula, soft palate, or pharyngeal wall
- cervical adenitis: neck edema
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Term
| What would the grey-white patch of exudate on the tonsils of a diphtheria patient be composed of? |
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Definition
| coagulum of fibrin, leukocytes, and cellular debris |
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Term
| What is a major clinical complication of diphtheria? |
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Definition
| mechanical obstruction of airway if the membrane separates from the trachea |
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Term
| What is the difference between the phage in Corynebacterium diphtheriae and Corynebacterium ulcerans? |
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Definition
| Corynebacterium ulcerans produces smaller amount of diphtheria toxin (milder symptoms) |
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Term
What parts of the body does Corynebacterium ulcerans infect?
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|
Definition
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Term
| What is Corynebacterium jeikeium and what does it cause? |
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Definition
opportunistic pathogen that infects immunosuppressed patients in the hospital:
- bacteremia, catheter infetions, artificial heart valve infections, wound infections |
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Term
| What is Corynebacteriumjeikeium resistant to? |
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Definition
| ampicillin and cephalosporins |
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Term
| What is the appearance of Listeria monocytogenes on a Gram stain? |
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Definition
| Gram-positive rods resembling diphtheroids |
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Term
| What does a colony of Listeria monocytogenes look like on a blood agar plate? |
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Definition
narrow zone of beta hemolysis
catalase positive
characteristic tumbling motility |
|
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Term
| What are some reservoirs for Listeria monocytogenes? |
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Definition
| soil, water, decaying vegetation, animals (esp. dairy), asymptomatic humans (5-10%) |
|
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Term
| Where do Listeria monocytogenes grow and what three proteins does it use to move |
|
Definition
In macrophages:
internalin for cell attachment
listeriolysin for movement within a cell
host actin for moving to new cells |
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Term
| What are some clinical conditions associated with Listeria monocytogenes? |
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Definition
- meningitis in immunocompromised patients
- spontaneous abortion in pregnant females
- bacteremia and meningitis in neonates
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Term
Why is Listeria monocytogenes particularly good at causing food-borne outbreaks?
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|
Definition
| It survives and grows in the cold (4 degrees C) so it can contaminate dairy food |
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Term
How is Listeria monocytogenes diagnosed in the lab?
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|
Definition
- Gram stain of the CSF (should see intracellular Gram-positive rods in macrophages and neutrophils)
- colonies look like beta-hemolytic strep, but:
- are catalase-positive
- sensitive to streptomycin
- may have tumbling motility
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Term
| What is observable about the unusual motility of Listeria monocytogenes? |
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Definition
In motility agar stabs it forms an umbrella of turbidity
In broth it produces tumbling motility |
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Term
| Where are erysipelothrix rhusiopathiae found? |
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Definition
| in animals, meat, and seafood |
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Term
| How can one get erysipeloid? |
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Definition
Following traumatic inoculation of the skin (associated w/ fishermen, butchers, and veterinarians)
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Term
| How is erysipeloid treated? |
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Definition
| penicillin or erythromycin |
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Term
| What are diagnostic characteristics of erysipelothrix rhusiopathiae? |
|
Definition
- positive for hydrogen sulfide
- "test-tube brush" motility
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Term
| Which of the diphtheroids is anaerobic? (2) |
|
Definition
Lactobacillus: aerotolerant
Propionibacterium: can't grow well aerobically |
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Term
| What is the appearance of Lactobacillus acidophilus? |
|
Definition
long, Gram-positive rods in chains
looks like viridans streptococci |
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Term
| Where are Lactobacillus acidophilus considered a normal flora? |
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Definition
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Term
| How is Lactobacillus acidophilus associated with a healthy vagina? |
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Definition
| Absence of Lactobacillus acidophilus allows the overgrowth of Gram-negative anaerobes, such as Gardnerella vaginalis, which is associated with vaginitis |
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Term
| How is vaginitis diagnosed? |
|
Definition
- Gram stain of vaginal sample (count # of lactobacilli)
- pH test of vaginal secretions (check for loss of acidity)
- "Sniff" test of vaginal fluid: add KOH to release aromatic amines if present
- NOT culture
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Term
| How is Propionibacterium an opportunistic pathogen? |
|
Definition
| It is a normal skin flora and common blood culture contaminant that can cause endocarditis, infected implants, wound infections, abscesses |
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Term
| What other normal skin flora is Propionibacterium similar to in pathogenicity? |
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Definition
| coagulase negative Staph (i.e. Staphylococcus epidermis) |
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Term
| What are some characteristics of Bacillus species? |
|
Definition
- gram-positive rods
- spore forming
- grow best in air
- catalase positive
- motile
- old cells may stain Gram-negative and mislead clinicians
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Term
| What do both Bacillus subtilis and bacillus cereus cause? |
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Definition
| systemic infection w/ bacteremia, and wound infections in immunocompromised patients |
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Term
| Which species, Bacillus subtilis and bacillus cereus, is responsible for food poisoning? |
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Definition
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Term
| What do Bacillus subtilis and bacillus cereus look like on blood agar plates? |
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Definition
| greyish-white beta-hemolytic colonies |
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Term
| What are two toxins produced by bacillus cereus? |
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Definition
| enterotoxin and pyogenic toxin |
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Term
| What are typical foods involved in bacillus cereus food poisoning? |
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Definition
| "food warmer" foods (i.e. meats in gravy, fried rice) |
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Term
| How are humans infected by Bacillus anthracis? |
|
Definition
- skin contact with infected articles
- breathing spores from wool/goat hair
- eating spores or infected meat
- rare in humans, common in animals
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Term
| Where in the US and in what occupations is anthrax usually seen? |
|
Definition
in the Southwest near Mexico
farmers, ranchers, butchers, vets, tapestry-weavers |
|
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Term
| What are three anthrax virulence factors? |
|
Definition
- capsule is antiphagocytic
- lethal exotoxin and edema exotoxin (protein-carbohydrate complexes)
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Term
| How are the anthrax exotoxins activated? |
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Definition
| they need a protective antigen that binds and transports them into the host cell |
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Term
| What is the clinical consequence of cutaneous anthrax infection? |
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Definition
| half a day to 12 days after inoculation, an erythematous papule forms and grows until a black scab forms (complications include local edema, toxemia, bacteremia, death) |
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Term
| What is the clinical consequence of gastrointestinal anthrax infection? |
|
Definition
lesions at base of tongue or tonsils => sore throat, fever, regional lymphadenopathy
inflammation and lesions of intestines => nausea, vomiting, fever, pain, bloody vomit and diarrhea |
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Term
| What is the clinical consequence of pulmonary anthrax infection? |
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Definition
| initially: sore throat, mild fever, malaise, cough, muscle aches => then: difficulty breathing, shock, respiratory distress with cyanosis => massive edema of neck and chest |
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Term
| How do inhaled anthrax spores multiply in the host |
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Definition
| They reside for weeks in the alveolar recesses until taken up by macrophages, then germinate and replicate within the macrophages |
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Term
| Why is it difficult to treat anthrax with antibiotic prophylaxis? |
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Definition
| Inactive/latent spores are unaffected by antibiotics |
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Term
| How are non-pathogenic Bacillus colonies (not anthracis) distinguished on agar plates? |
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Definition
| dry, wrinkled, rarely mucoid, beta hemolytic |
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Term
| When should culture for anthrax be done? |
|
Definition
| in clinically ill ppl with fever, myalgia, and other non-specific findings |
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Term
| Which two places are inappropriate to obtain cultures from for anthrax detection/ |
|
Definition
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